Objective: To examine the mechanism of action on the effects of endotoxin on the growth of plasma cell tumor and to study the transport system controlled by insulin-cAMP in this tumor. Approach: Current studies involve effects of nonogram quantities of endotoxin on the development of plasma cell tumors in BALB/c mice. Long-term administration of minute amounts of endotoxin materially increase the rate and extent of tumor development. The biochemical basis for this effect is under study. Studies on plasma cell tumors in culture reveal an endocrine dependent system. cAMP inhibits growth, insulin reverses this inhibition although it has no affect on the growth of tumor cells in culture without cAMP. The transport systems controlled by this insulin-cAMP system is under study.